Explosive actuated driving device



EXPLOSIVE ACTUATED DRIVING DEVICE Filed NOV. 9. 1959 Fglg] INVENTQRS. Rabar't M Helm/0 4 y Char/es d. DaCaro ATTURNEY United States Patent 3,063,054 EXPLOSIVE ACTU TED DRIVING DEVICE Robert W. Henning, North Haven, and Charles J. De

Caro, Orange, C0nn., assignors to Olin Mathieson Chemical Corporation, East Alton, 111., a corporation of Virginia Filed Nov. 9, 1959, Ser. No. 851,834- 11 Claims. (Cl. 144.5)

This invention relates to improvements in explosive actuated tools and more particularly to a drivable unit therefor for carrying a working element, such as a fastener, to render the element captive, whenever necessary, in the event of any tendency to free flight from the tool.

Explosive fluid powered tools are useable to perform many functions such as cutting, punching, swaging, and also securing such as by driving fasteners of suitable toughness and hardness into steel, concrete and the like. These tools use a powder charge packaged conveniently in the form of a cartridge and loaded in an amount carefully designed to drive the working element, such as a fastening stud or pin, down the bore of the tool barrel for forcible projection from the muzzle of the barrel only a predetermined distance. For fastening, for example, where the predetermined distance extends into the surface of an object against which the tool muzzle is held, this requires a proper relationship between the size of fastener used, the resistance offered bythe work'and the explosive charge, all within permissible tolerances. While a bit of overdriving is permissible, it will be appreciated that excessive overpenetration is intolerable regardless of whether the overpenetration occurs from excessive explosive power or from an' unexpected insufficiency of resistance of the object acted upon by the working element. From both safety and tool maintenance viewpoints, it will be further appreciated that any tendency of-the driven element to be projected beyond the predetermined distance may not only damage the tool, but also may result in an undesirable projection of a run-awayworking element. .For this reason, it sometimes becomesvnecessary with heretofore available tools to? exercise a. great deal of rather burdensome care so that the force with which the driven element is projected be made adequate but never excessive and/or so that the object or objects to be acted upon by the working element offer a suitable expected resistance.

One of the objects of this invention, therefore, is to provide for explosive actuated tools a safety arrangement including a drivable unit normally capable of being returned and reused for further tool operation, but rendering any projectable element captive in the event considerable overpowering occurs and/ or the object to be acted upon offers too little resistance, either because it is too thin, or too soft, or too'far removed from the explosive actuated tool muzzle so that the projectable working element carried by the drivable unitencounters unexpected ease of penetration into the object, or objects constituting the target, such as objects which are to be associated together, for example by a fastener.

Another object is to provide a novel drivable unit in combination for operative association with a tool having means for arresting any explosively projectable element.

Another object is to provide for tools of this type a drivable unit with means for stopping the unit in such a way as to also avoid excessive shock and damage to the tool parts.

Another object is to provide a tool arrangement enabling operation which permits repeated use of the type of tool described with the utmost safetywith the least interference with the operation-and with the least'complication v 'ice in tool operation despite the presence of the safety features.

Another object of the present invention is to provide a novel slidable ram or piston for holding securely but detachably a working element to be driven through a tool barrel and capable of acting as a brake only whenever excessive projection is imminent.

A further object of the present invention is to provide a unit especially adapted for driving a fastener with means for stopping said fastener before any excessive penetration can occur while at the same time permitting normal tool operation despite a small, but tolerable penetration.

A still further object is to provide a novel ram especially adapted for detachably holding and driving a working element, and particularly for driving a fastener having a threaded connection, without damage to the threads.

Still another feature of this invention resides in the structure of the parts for providing safety as well as tool shock absorption including an expendable driving and braking element of long useful life and easy replace'ability.

Other features, objects and advantages of this invention reside in the arrangement and design of the parts for carrying out their appropriate functions, and these will become apparent from this description when taken in connection with the accompanying drawing in which:

FIG. 1 is a fragmentary side view in partial cross section showing one embodiment of the driving unit or" this invention in the normal fully driven position in a suitable fastener driving tool, for example, positioned at a work surface of an object into which'fasteners are to be driven;

FIG. 2 is a longitudinal view in cross section showing the structure of the driving and braking element of FIGURE 1 for forming a drivable unit with a working element;

, FIG.- 3 is another longitudinal cross sectional view showing another embodiment of the driving and braking element of this invention; and H FIG. 4 is a longitudinal View partly in cross section showing a modified form of driving unit for carrying another .type of threaded fastener. v In accordance with this invention there is provided a driving and braking unit constructed so as to dissipate in the .unit only the energy of excessive overpenetration while permitting a tolerable amount of overpenetration of .the type occasionallyencountered as the result of normal variation. The unit comprises a driving and bralcing cylinder or piston element designed to take. up theenergy of excessive penetration by plastic deformation. The element of this invention is especially adapted for combination with -a suitable arresting device on a driving tool adapted for receiving the unit ina barrel bore. One such arresting device involves swinging jaws such as those described in connection with copending application Serial No. 736,759, filed May 21, 1958. Another suitable arrester has spring fingers shown in FIG. I mounted on a portion of a tool otherwise having, like above noted Ser. No. 736,759, the slidable and spring biased tool action and construction described in US. patent application Serial No. 355,034 filed May 14, 1953 by Kopf, Henning and Marsh now US. Patent No. 2,945,236, granted July 19, 1960. 'It will be understood that while this typeof tool action and construction is preferred this invention has utility with any other type of tool having a suitable piston arrester. 1

The cylinder or piston is provided on its rear end with a-relatively plastic portion adapted for fitting the barrel bore and for taking up all of this excessive energy byv its deformation. Accompanying this portion is a front portion which is smaller to avoid deformation of the latter by said jaws and preferably which is relatively'hard and :rigid and serves to prevent deformation in the .unit in the event of an occasional normally occurring slight overpenetration. Particularly useful is the arrangement of this invention for the driving of threaded studs, especially those with only a rather small length threaded at their rear end trailing a pointed piercing front portion for protruding from the work surface into which the stud is explosively impaled and upon which an object is to be fastened threadedly at the protruding threads.

To accomplish the desired result the piston or cylinder is formed with a front end portion not only harder than the rear end but also of reduced transverse cross sectional size as compared to the bore-fitting rear end. The front end thus forms on the rear end a sub-caliber frontal extension of a size small enough to pass the arrester. Any sub-caliber working element such as a fastening stud is detachably connected in any suitable way, but preferably by suitable screw threads, in a recess preferably, to the front of this extension.

The front and rear portions may be either integral or two parts joined together permanently, preferably the former except where a maximum differential in deformability is desired. When integral the deformability diiferential is obtained by making the driving and braking element of the unit of suitable steel or iron subjected to local annealing, carburizing work hardening and heat hardening. When made of two parts the front part or holder is a suitable steel about as tough and hard as a fastener, for example, while the rear part, i.e. the piston part of full caliber, may be of any easily deformed material strong enough to restrain a fastener or other Working element. Dead soft iron, soft steels, copper and aluminum or suitable alloys thereof of an extrudable character are contemplated. The unit is preferably coated oer plated to avoid corrosion and/ or for lubrication. A copper coat is suitable. Whatever the material employed, a cohesive arrangement is contemplated so that the piston will cohere upon impact and not tear apart to allow the fastener element to project dangerously.

Braking occurs only when overpenetration becomes excessive and poses a real danger, because the extension defers the association of the piston arrester and the full size deformable rear part of the piston. This arrangement avoids putting the safety arrester parts of the tool into operation upon the driving piston and its captive working element for each and every slight overpenetration which normally occurs occasionally without involving any danger at all. Thus, the safety parts of the tool are not overworked and their replacement is deferred and/or maintenance is correspondingly reduced. How this is done is either apparent from or explained in connection with the following description of various preferred embodiments.

The description proceeds with reference to a tool of the general type shown in above identified patent of Kopf, Henning and Marsh with an arrester somewhat modified from that shown in above noted Serial No. 736,759.

The rigid extension, recessed or not, spaces the deformable piston rearwardly sufliciently from the projected working element to avoid oversensitivity to overtravel. Its support reduces fish-hooking of the element.

It permits impacting at the bottom of recesses into which the tool muzzle cannot enter.

In the embodiment shown in FIGURES l and 2, the fastener 1 is shown carried at its extenal threads 2 by a driving unit consisting of a relatively undeformable internally threaded fastener holder 3 and an enlarged separate relatively soft piston 4 of a diametral size of full caliber for fitting the bore 31 of the barrel 30 of the typical tool shown in FIGURE 1. Here piston 4 is received snugly but slidably for explosive fluid driving toward the tool muzzle 32 at which there is mounted suitable unit arrester or interceptor members such as the plurality of flexible jaws 33 and 34 normally sprung outwardly and secured in a circumferential array to the tool. This is done in a manner adapting the front end of the slidable tool shield 70 to be held in abutment with the workpiece 75 against the bias of shield spring 71 pushing on snap ring 72 on the shield tube 73 telescopically mounted between tool barrel 30 and tool housing tube 35. For convenience in releasing the safely driven element from the tool jaws, there is also mounted on shield 70 a resilient catch 38 extending rearwardly and having a sear 37 biased for engagement with the series of notches and detents 39 formed on the side of the housing tube 35 and for manual disengagement by use of the finger release 40 to release the cam ring 74 for coaction with the jaws again.

Jaws 33 and 34' are the ends of resilient appendages 33 and 34 of a ring-like base screw threadedly mounted at threads 36 on the barrel each appendage biased for spring outwardly to leave a large enough muzzle opening to clear the drivable unit for separation from the tool, unless the tool and its housing is thrust forward over the barrel 30 with the jaws 33 and 34', and shield 70 held in abutment with the workpiece surface. In this position the shield 70 and front of housing tube 35 are in abutment with each other, and finally with the jaw confining cam ring 74 carried on the shield and its tube for cainming the jaws inwardly to form a restricting orifice large enough to pass not only the fastener 1 but also the holding extension 3, if necessary, but not large enough to pass the soft piston part 4. This normally stops spaced no further than the position shown in FIGURE 1 although it may get closer to the jaws by the length or fractional part of the length of the holder. In any event piston 4 usually remains spaced from the jaws, not only after underpenetration but also upon tolerable overpenetration or overtravel. Upon excessive overtravel, abutment against the new closed jaws and braking deformation occurs by extrusion along circumferentially spaced longitudinally extending regions along the sides of the brake piston 4 beginning at the bevel 5. These correspond in number to the jaws and make indentations with intervening ribs corresponding to any resultant circumferential spacing or out of roundness between the jaws. For this purpose grooving. or other irregularities from the cylindrical shape can be provided.

This allows the jaws to coact with the piston locking it and the holder 3 against rotation so that the tool and captivated piston together may be unscrewed from the overpenetrated fastener in order to readily extricate the tool from the work in the event an overshot threaded fastener becomes stuck in the work.

Holder 3 and the soft deformable piston 4, beveled preferably at 5, are joined by any suitable extension from one into the other, such as holder shank 6 having threads 7, or the like, for receipt into the piston recess 8, correspondingly but more fully threaded at least adjacent the closed base 9 of the recess, thereby permanently fixing the holder on the front of the piston adjacent the bevel 5 with the holder and piston abutted at least at the separating shoulder 10 next to bevel 5 if not also abutted at the recess base 9.

'For a /4 inch threaded fastener, the fastener holder 2 constitutes an extension of reduced diameter of about 0340-0345 of an inch fixed on the front end of a piston 3 held at a closer tolerance to a diameter of about 0.422 of an inch so as to permit the piston to fit a barrel bore only a few thousandths of an inch larger. The holder 2, being rigid, is sutficiently reduced in size so as to clear the jaws 33' and 34 at all times, i.e. when the jaws are either open wide or closed. The diametral size of the piston, however, is such as to clear the jaws only in their open position so that, when the jaws are closed, they define a safety orifice about 0.368 of an inch, or somewhat less by a few thousandths, but in any event sufiicient for braking the size of fastener propelled even with the heaviest powder load for that fastener size. It will be understood that as the size varies the dimensions of the drivable unit will vary correspondingly. The unit is sized to cohere, i.e. the diameters are made adequate to resist the unit pulling apart under the. action of the tool jaws.

'During normal tooloperation, the fastener, detachably secured in the front recess 11, is preferably always at least fully passed as shown in FIGURE 1. The holder may be projected up to the orifice as shown or a bit farther but not the piston. Recess 11 is threaded to a length somewhat less than the nominal thread diameter of'the stud 1. A A--20 NC thread is suitable.

The front end of the piston is preferably beveled at 5 to a cone angle of about 30 so that upon its abutment with the jaws the abutted piston encounters a gradually increasing resistance to passagethrough the closed jaws which perform an extrusion operation on the piston part to gradually stop the entire drivable unit including the stud 1. The bevel angle corresponds to the entry or throat angle of the orifice defining jaws.

To obtain the desired safety braking action together with gradual stopping the piston 4 is made considerably softer than the holder 3, the latter being at least the same toughness and hardness as-the fastener. The piston is, therefore, made of a relatively soft and malleable material cap-able of adequate elongation so as to adapt the piston to an'extruding, raking or ironing action in'the arresting jaws but one strong enough to resist fracture and fastener'es'c ape. A suitable: piston material is soft metal having a hardnessof about 30 Rockwell C and having a suitable toughness for the purpose. When of suit able steel, a length-ofabout 1%.is adequate." I Apart from its shank 6, the holder 3extends forwardly for more than A of an inch but not more than about one inch. This length together'with a hardness suitable for the purpose, suchas from about to about 57 on the Rockwell C scale provides for considerable ov'erpenetration so that substantially no interfering holder deformation occurs and so that no cylinder deformation occurs for fastener braking for'example, unless a full andserious run-away is progressing toward free flight, and there is no chance that any reasonable expected residue of target resistance is adequate to stop the fastener and render the fastener harmless,;although somewhat overpenertated.

As long as it remains undeformed, cylindrical piston '4 and its holder 3 areagain ready after being screwed from the' fastener 1, shown impaled inworkpiece 75, for assembly with another fastener to make a drivable unit for the ensuing shot or shots. q v f a In the embodiment of FIGURE 3, the driving and braking" unit apart from .the fastener 1, is a single piece of suitable material, such as a low carbon heathardenable steel. The front 'end43 isa reduced extension treated to a suitable hardnessof about from to 5S on the Rockwell C scale. The rearor' deformable piston end 44 is :an'enlargement left .or' made soft and. integral with the reduction 43 extending fora suitable standoff distance for the part 44, 'the ends extending into one another at the bevel shoulder sloped at .about a 15 angle, to form a 30 die entry cone angle. Reduced end 43, as in the previous embodiment has athreaded frontrecess 41 for detachably securing a fastener with the least length of thread for protrusion as well as forgreater lengths. The completed drivingfasteningunit is shown overpenetrated into the body of the workpiece 85. By untwisting the unit from fastener 1, independently from the tool, the unit is ready for reuse relatively unchanged and without further ado. The-dimensions are those of the previous embodiment.

The embodiment of FIGURE 4 illustrates a unit including an internally threaded type of sub-caliber fastener 101 connected at the threaded spigot 51 to the relatively rigid holder 53 having in turn a holder shank 56 knurled at 57 :and force fitted in permanently fixed relationship in piston recess 58 upon the front end of the deformable piston .54 enlarged to full caliber size.

The projected transverse area of the rigid extension, of this and other embodiments, is preferably sufficiently broader than that of a penetrating element to normally provide an abutting shoulder acting as a penetration limite'r effective at mild degrees of overpenetration.

To provide various shapes of counter bores about driven fasteners, the extension may be of a complementary shape and is intentionally overdriven'to a controlled degree; One extension may bebeveled at theleading edge to give a conical countersink or it may be square or even of more complicated shape instead of round.

From the foregoing description of embodiments heretofore believed preferred it will be understood that while there are shown for round barrel bores, other shapes of bores may be used and that those skilled in the art may make various changes and many other modifications without departing from the spirit and scope of this invention as set forth in the appended claims.

What is claimed is:

l. A driving piston having'a portion of plastically deformable material for driving a working element at least to but not excessively beyond a predetermined projected position with respect to an impact tool of the explosive actuated type having a barrel bore for receiving said piston for movement toward the barrel muzzle and having a piston arr'ester adapted toforrn a sufiicient restriction in said bore adjacent said muzzle to initially retard and finally stop said piston in its movement beyond said restriction byplastically deforming said portion, said, piston having axially secured thereto permanently a front portion with means for detachably securing said element to said piston in sufficiently forwardly spaced relationship of said element with respect to saiddeformable portion to adapt said portions'uponlarrest to form a link of cohesive material between said element and restriction .while permitting said element to reach at'le'ast said predetermined position and said front portion projecting sufiiciently forwardly of said deformable portion to allow said element to reach not excessively beyond said position before said restriction begins to arrest the piston, said deformable por' tion being enlargedv relative to said restriction and said front portion being small relative to said deformable portion and of reduced size to pass said restriction.

2. A studdriving piston for slidable reception in 'an explosive .charge actuated studdriving tool of the type .described having an orificed piston interceptor means adjacent the muzzle of the tool movable between opposite positions in one of which said means is operable as'an extrusion die in the event of overp'enetration of said stud into a workpiece, and in the other of which said means forms a larger opening, said piston having a relatively rigid anterior portion secured against axial separation permanently to a posterior portion plastically deformable -by said 'die in said one position, said anterior portion being recessed at its front end for captively receiving .the 'normally unimpaled trailing end of. a stud in detachable relationship with respect to the piston and in forwardly'spaced relationship with respect to said deforma- .ble portion sufficiently to adapt'said' portions upon arrest to form alink of cohesive material between said stud and die, said anterior portion being of a size adapted to pass through the die while said posterior means is of a large enough size to pass only'through the larger interceptor means opening for-adaptingsaid piston for reuse'so long as said posterior portion remains undeformed.

3. In an impact tool ofthe explosive actuated type, the combination of a barrel with a bore, a piston member movable in said bore and having a forwardly extended rigid portion with means for carrying a working element in rigid alignment with the bore and secured thereto permanently an enlarged portion of relatively plastically deformable character of a size for movably mounting said member in said bore with suflicient obturation to be actuated by propellent gas of said explosive, an impacting working element detachably secured by said carrying means on said extended portion in less than the full caliber of said bore for projection therefrom about a predetermined distance, and means adapted to form a restriction in said bore for passing only part of said enlarged portion by extrusion, ironing and the like for exerting a drag on said assembled member and element thereby bringing the movement of said member from said bore to a stop gradually, said extended portion being of reduced size to pass said restriction and being of suflicient length extending forwardly of said deformable portion to secure said element and deformable portion with the latter spaced rearwardly from said element sufficiently to maintain said deformable portion spaced from said restriction when said element is projected from said bore any distance within said predetermined distance.

4. In an explosive actuated stud driving tool, a barrel having a bore, a piston of a relatively malleable material adapted to move slidably through said bore, a rigid threaded member permanently secured axially to said piston forming with said piston a cohesive link detachably connecting a threaded stud to said piston in rigid alignment with said bore for stud projection forwardly of said piston to not more than a predetermined distance beyond the muzzle of said barrel, and means at said muzzle for reducing one part of said piston by plastic deformation only in the event of movement of part of said piston beyond said means whereby said link by its cohesion gradually arrests said stud prior to its projection beyond said predetermined distance and finally stops it by abutment of the remaining unreduced part of said piston with said means, said member extending forwardly of said piston and being of reduced size to pass said means.

5. In an explosive actuated stud driving tool, a barrel having a bore, a piston adapted to move slidably through said bore of a relatively malleable character at the rear end and of a relatively rigid character at the front end adapted for detachably connecting a stud to said piston against axial separation therefrom and in rigid alignment with said bore for stud projection to not more than a predetermined distance beyond the muzzle of said barrel, a forwardly facing and converging exterior bevel between the ends, and means at said muzzle for reducing said bevel and only part of the rear end of said piston by plastic deformation only in the event of movement of said part of said piston beyond said means, said piston forming a cohesive link between said stud and reducing means thereby said link by its cohesion gradually arresting said stud prior to its projection beyond said predetermined distance and finally stopping it by abutment of the remaining unreduced part of said piston with said means, said front end being integral with said rear end and being of reduced size to pass said means.

6. A drivable unit adapted to be driven through the bore of the barrel of a powder actuated stud driving tool having run-away unit interceptor means adapted to form a restriction in said bore adjacent the barrel muzzle at least during driving, said unit comprising a stud carrier adapted to hold a stud with a forwardly projecting piercing portion in rigid alignment with said bore for penetrating a workpiece when said carrier is driven in said bore by said powder from the barrel breech to adjacent said muzzle of said barrel, said carrier including a relatively deformable body of a size adapted to fit said bore fluid drivably and to adapt said body for plastic reduction by said means, and also including a rigid relatively undeformable coupling secured permanently against axial separation to the front of said body and having a recess for detachable connection to said stud back of said piercing portion, said coupling being of a size smaller than both said bore and said body for adapting said coupling to clear said interceptor means, said body and coupling formed of material adapted for cohesively linking said stud and restriction.

7. The unit of claim 6 wherein the recess is threaded for connection with a complementary thread on the stud back of the forwardly projecting piercing portion;

8. The drivable unit of claim 6 whereinthe front end of the body adjacent the coupling is beveled from the size of the coupling to the full size of the body.

9. The unit of claim 6 wherein the body is of one relatively malleable material and the coupling of another and relatively rigid material to obtain the maximum difference between the deformability of the one and the rigidity of the other.

10. The unit of claim 6 wherein the hardness of the body is around Rockwell C while that of the coupling is around 50-55 Rockwell C.

11. A drivable unit for a fastener adapted to be driven into a workpiece surface through the bore of the barrel of a powder actuated tool with a plurality of articulating interceptor means, said tool having a cam surface and said interceptor means having follower surfaces responsive to relative axial movement between said cam and follower surfaces for rendering said means movable between a smallest opening forming a conical restriction in said bore adjacent the barrel muzzle in response to said movement by tool abutment squarely with said surface as a condition precedent to driving, and a largest opening at least as large as said bore, comprising a fastener car-rier adapted to hold a threaded fastener with a forwardly projecting piercing portion in rigid alignment with said bore for penetrating said workpiece when said carrier is driven in said bore by said tool from the breech to said muzzle of said barrel, said carrier including a relatively deformable rear portion of a size adapted to fit said bore slidably for movement therein and removal therefrom and adapting it to be reduced over only part of its length plastically by said interceptor means only in the event of movement of said carrier forwardly beyond said interceptor means during driving and also including a rigid relatively undeformable coupling portion extending forwardly from the front of said deformable portion and having internal thread means for detachably receiving the threaded part of said fastener back of said piercing portion in a recess in the front of said coupling, the front end of said portion adjacent the coupling being beveled forming a forward facing cone angle of about 30 complementary to that of said conical restriction, sa'd coupling being of a size smaller than both said bore and said body for adapting said coupling to clear said interceptor means.

References Cited in the file of this patent UNITED STATES PATENTS 2,663,259 Catlin et al. Dec. 22, 1953 2,925,602 Kopf et al. Feb. 23, 1960 FOREIGN PATENTS 167,800 Australia June 6, 1956 1,210,004 France Sept. 28, 1959 

